1. Field of the Invention
The present invention discloses another method that employs micro photo etching technique used in semiconductor manufacturing to fabricate a plurality of molds then stacking up and electroplating the molds to form a multiple-lead punch die for producing microparts.
2. Description of the Prior Art
Traditional ways of manufacturing microparts generally include optical projective wheel grinding and wire cutting EDM (Electro-Discharged Machining). These methods use mechanical machining to make the parts to the required dimension. As mechanical machining has its inherent precision limitation, it usually is difficult or impossible to produce the microparts in large quantity while still maintain high degree of dimensional precision.
Another traditional way to produce microparts in large quantity is through punching process that uses molds such as punches, strippers and die plate. However the molds usually have to be made by mechanical machining which has precision problem set forth above. Moreover the machining stress and residual stress becomes another factor making precise dimension difficult to attain.
Nevertheless using punch molds for producing microparts is still a widely used method. This method includes to fabricate single or simple parts by mechanical machining, then assemble the parts to become molds such as punches, strippers and die plates. However this method introduces other type of problems. One is that it needs multiple working stations to perform all the machining required. Production time and cost become higher. Another problem is that the pitch between leads is large due to mechanical factors. It therefore becomes very difficult to produce large number of leads within a small dimension. All this becomes serious issue to be resolved when trying to mass produce microparts with high precision at low cost.
FIGS. 1 and 2 illustrate an example of the traditional ways set forth above. A press board 1 consists of four different mold plates (FIG. 1A). Each mold plate has one or more guided hole 10 which is formed by wire cutting EDM (FIG. 1B). The mold plate may also consist of an upper mold plate 12 and a lower mold plate 14 which are made respectively by optical projective wheel grinding and then be assembled together (FIG. 1C).
FIG. 2 illustrates a mold assembly made by the pressboard shown in FIG. 1. There is a fixed board 20 which has a plurality of screw holes 28 and grooves 29 formed therein. A punch 15 for a guided hole 16 is mounted on a groove. Each punch 15 has a slant section 18 adjacent the guide hole 16 and a key way 24 adjacent the groove 29. A metal key 22 engages with the keyways of the assembled punches and being fastened tightly to the fixed board 20 by means of screws 26 engaging with screw holes 28.
FIG. 3 illustrates the method of using LIGA technique to make molds for producing multiple-lead microstructures disclosed by Applicant in U.S. Pat. No. 5,645,977. It includes disposing a layer of resist 30 on a base plate 33. Then a mask 31 is placed above the resist 30. A X-ray (or ultraviolet light) 32 is employed to project upon the mask 31 to form a lead punch 34 in the resist layer 30 (FIGS. 3A and 3B). Then an electroplating process is performed on the lead punch 34 to form an electroforming metal layer 35 thereon (FIG. 3C). Finally, the base plate 33 and the lead punch 34 are removed to obtain the electroforming metal layer 35 with lead dies 351 formed therein.